The main purpose is that before the SCAN was introduced you had to connect using a TNS entry that listed every VIP in the RAC, so if you add or remove nodes, the TNS entry had to change. That's a pain in the ass, especially for dynamic environments. SCAN allows your TNS entry to contain a single address, no matter how big or small your RAC environment. It is a much simpler solution from a client configuration perspective.

The SCAN doesn't do anything new compared to the previous RAC setup. The old RAC setup did load balancing also. The point it, it simplifies things.

I don't believe RAC does anything mysterious apart from this. Maybe the interviewer was mistaken and thought it had some other value. Maybe they were pressing you to see what your reaction would be. You can tell a lot about a person by the way they react to such things. I'm always honest and would say something like, "If it has any other value, I don't know what it is. What do you think is does apart from what I've said?"